We propose to study experimentally the physical-chemical processes controlling the growth of hygroscopic medicinal aerosols in the human respiratory tract and to use the results to refine and apply existing theoretical aerosol growth models to the respiratory tract. These processes include the intensity of the turbulence in the inhaled air, the rate of air mixing, humidification and temperature equilibration of the inhaled air in the airways, and the growth inhibition or acceleration properties of surface active chemicals. Mathematical models currently used to predict the deposition sites of inert and hygroscopic aerosols in the human respiratory tract will be tested by experimentally measuring the quantity of aerosol deposited throughout hollow casts of human airways, in the lungs of artificially ventilated dogs, and in the lungs of human subjects. Studies in hollow casts of single and multiple airway generations will evaluate the influence of airway dimensions and bifurcation geometry, steady and realistic oscillatory flow, and the shape of the laryngeal orifice on the quantity and pattern of deposited particles within each airway generation and bifurcation region. These mathematical models will be improved by incorporating the refined aerosol growth model and by using the results of these deposition studies. A physical model will be developed to simulate the total deposition and regional distribution of inhaled aerosols. Components of the simulator are aerosol characterizing instruments whose particle collection efficiencies match those of respective compartments of the human respiratory tract. The simulator will be invaluable in evaluating and optimizing the performance of commercial therapeutic aerosol generators. Studies with human asthmatics will evaluate if the chemical growth inhibitor, glycerin, causes any difference in the pulmonary function response and deposition patterns of subjects exposed to a commercial bronchodilator aerosol.